Under conventional growth conditions plant suspension cultures senesce and die shortly after reaching their peak biomass. This sudden death curtails the synthesis of any secondary products that may normally be produced in mature cells. Herein may lie a major reason for the inability of previous workers to secure desired secondary products from plant cultures. The ideal conditions necessary for prolonging the life span of mature tissue culture cells will be established. This will be accomplished by examining the senescence of plant suspension cultures subjected to various factors such as nutrients, hormones, inhibitors, and oxygen which are known to influence the senescence of whole plants. The influence of senescence on secondary product formation will be determined by studying the kind and quantity of phenols synthesized by rapid and slow senescing cultures.